by Kelly Hotard
A key principle of biological science is the interdependence of life – the idea that every living thing on Earth plays a delicately balanced role in the survival of other organisms in the ecosystem.
In the Department of Pathobiological Sciences at LSU’s School of Veterinary Medicine, or SVM, researchers examine the damaging domino effects that result when these relationships are disrupted by deadly viruses and diseases. Armed with extensive knowledge of these pathogens, the scientists search for cures and create medicines, often in the form of vaccines, designed to combat the illnesses.
Of course, before vaccines can be introduced for public use, they must undergo rigorous testing and receive licensing permits from the U.S. Department of Agriculture, and pharmaceutical companies must agree to sell and distribute the medicines. It’s a lengthy, complex process that begins in LSU’s Office of Intellectual Property, Commercialization and Development, which helps the researchers secure patents for their vaccines with the U.S. Patent and Trademark Office.
LSU SVM scientists have recently filed three patents for vaccines that treat a wide range of ailments and patients, from respiratory infections in cattle to herpes viruses in humans. Researchers at the school are also working on two projects that will lead to patented vaccines.
Bovine Herpes Virus
Shafiqul Chowdhury, professor of molecular virology, has developed a recombinant vaccine for bovine herpes virus type 1, or BHV-1, a pathogen in cattle that can cause severe sicknesses such as infectious bovine rhinotracheitis and bovine respiratory disease complex, more commonly known as shipping fever. Complications from these illnesses include abortion in pregnant cows, fatal pneumonia and substantial drops in milk production, all of which result in a $500 million annual loss for the U.S. cattle industry alone.
What makes BHV-1 so difficult to treat, Chowdhury said, is the virus’ ability to establish lifelong latency after the initial infection. Even the modified viruses used for existing BHV-1 vaccines, in which a gene is deleted from the viral DNA, can resurface at times when the animal’s immune system is weakened, such as during periods of stress.
Chowdhury’s vaccine, however, contains an engineered virus lacking the envelope proteins that suppress immune response. This virus also cannot reactivate from latency.
“Recently, we have completed a small-scale vaccine efficacy study and compared our vaccine candidate relative to the current gE-deleted marker vaccine,” said Chowdhury. “Based on the results, calves vaccinated with our vaccine induced considerably improved protective immune response when compared with the current vaccine.”
The Chowdhury laboratory, with support from Elanco, a global animal health company, is
now developing a serological marker test for the vaccine, which is required for the European market.
LSU SVM researchers treat all manner of animals, both on land and under water. John Hawke, professor of aquatic animal health, along with former LSU graduate student Esteban Soto, has created a vaccine that protects warm- and cold-water cultured and wild fish, such as tilapia, against Francisella, a species of emergent bacterial pathogens. In recent years, these bacteria have caused acute to chronic disease and even widespread mortality among fish in the United States, Taiwan, Costa Rica, Latin America, Norway, Chile and Japan.
Because tilapia are a hugely marketable food commodity, they are raised in farms all over the world. This high-density environment, however, also makes tilapia more susceptible to francisellosis. The disease produces tumor-like granulomas in the fish’s liver, spleen and kidney.
Hawke’s vaccine is a live-attenuated mutant form of the parent bacteria strain, capable of infecting the fish with a mild form of the disease that is cleared in a short period of time. The induced immunity generates a heightened cellular and long-term humoral response to Francisella in the fish.
Vaccinating tilapia is quite unlike inoculating humans or other animals. Rather than injecting the fish directly, the vaccine must be administered into the water. Month-old fingerlings are then immersed in the water, where they take in the vaccine through their gills and skin directly into the bloodstream. Hawke’s vaccine usually affords the fish at least a year of protection from francisellosis.
“The vaccine would be part of an overall health management system that would include biosecurity, improved husbandry practices, proper nutrition and water quality management,” said Hawke. “The goal is to reduce the dependence on chemicals and antibiotics in fish production.”
Hawke is seeking to partner with a pharmaceutical company to distribute and market the vaccine.
Ron Thune, who heads the Department of Pathobiological Sciences and is also a professor of aquatic animal health, has been making significant strides since the late 1990s on vaccines that protect catfish from a serious bacterial pathogen called Edwardsiella ictaluri. This pathogen causes a disease known as enteric septicemia of catfish, or ESC, which can cost the aquaculture industry as much as $40 million a year.
Thune began by testing a killed vaccine against E. ictaluri, which showed low efficacy against the virus and required multiple exposures. But by studying the rapidly invasive nature of the pathogen during these trials, Thune was able to develop a live-attenuated vaccine that could inject itself into the catfish and provide strong protection against E. ictaluri. A patent application was created, but because the vaccine strain only persisted in the fish tissues for two to four days, the product could not be successfully transitioned to field conditions and produced for commercial use.
“It became apparent that a deeper understanding of the way this bacterium causes disease is required,” said Thune. “So, during the next several years, with funding from the USDA’s competitive grant programs, we developed a model that began to explain the process. At present, the model explains the initial stages of infection, when the bacterium establishes itself as an intracellular pathogen in host immune cells known as macrophages.”
Thune’s ongoing research entails establishing subsequent stages of the infection, when researchers believe the bacterium is able to manipulate the metabolic activity of the host cell to the bacterium’s advantage. This has already led to the development of an initial live vaccine strain that persists longer after vaccination without causing disease and is effective following a single immersion exposure. Further research suggests the initial strain can be improved, and Thune is working toward this goal.
While the above epidemics affect people in an indirect way, LSU SVM researchers also develop remedies for human ailments. Konstantin G. Kousoulas, professor of virology and biotechnology and director of the SVM’s Division of Biotechnology & Molecular Medicine, has engineered a vaccine that protects against herpes simplex infections.
“Our herpes simplex virus vaccine is based on our work toward understanding how the virus enters into cells and spreads from one cell to others,” said Kousoulas. “The hallmark of herpes simplex virus infections is that the viruses enter neurons, where they stay latent. The virus reactivates from latency upon exposure to an external stimulus such as stress during exams, heat or the general status of the immune system.”
The Kousoulas laboratory found that modifications in viral glycoprotein prevent the virus from entering neurons, both in cell cultures and in animal experiments. Kousoulas’ vaccine, which contains a weakened virus that does not express this glycoprotein, protected mice from lethal challenge of herpes simplex.
“Having a live-attenuated vaccine that is safe, since it will not enter into the neurons, is the most attractive aspect of this vaccine,” said Kousoulas. In addition, Kousoulas’ vaccine, unlike existing herpes remedies, may also be used for therapeutic treatment of recurrent infections in people who have previously contracted the virus.
Kousoulas expects the vaccine-protection studies will be published soon.
Onchocerciasis and lymphatic filariasis
LSU is one of four universities collaborating on a more than $5 million project supported by the National Institutes of Health to develop vaccines for two neglected tropical diseases, or NTDs, called lymphatic filariasis and onchocerciasis, or river blindness. These illnesses are caused by nematode parasites and are usually transmitted to humans through mosquito bites. While lymphatic filariasis and onchocerciasis are severely debilitating on their own, they can also increase susceptibility to fatal diseases such as HIV/AIDS, malaria and tuberculosis.
The groups of researchers are producing a series of molecularly defined parasitic proteins in two animal models – the human parasite Onchocerca volvulus, a causative agent of river blindness, and Brugia malayi, a causative agent of lymphatic filariasis – that will be tested for efficacy in guarding against experimental infections. Molecularly defined vaccines against nematode parasites do not currently exist, and the vaccines being used to disrupt transmission of the diseases have shown signs of ineffectiveness because the parasites are growing resistant to them.
Thomas Klei, Boyd Professor of Parasitology and Veterinary Science and interim vice chancellor of research and economic development, is principal investigator for LSU’s portion of the team, which maintains a life cycle of B. malayi and conducts experiments with these recombinant proteins.
“Onchocerciasis and lymphatic filariasis are devastating diseases to hundreds of millions of people in tropical developing countries of the world,” said Klei. “These are mostly poor populations and diseases unique to them are generally neglected as compared to conditions of the developed world, hence the categorization of ‘neglected tropical diseases.’ A vaccine designed to greatly reduce the prevalence of NTDs would be an enormous step forward in improving world health, and our team is making progress in this direction.”
Klei said when the researchers find significant protection in both models of the molecularly defined proteins, phase one trials for safety in humans can begin.
Whether people will benefit directly or indirectly from these vaccines, the innovative work of scientists at LSU’s School of Veterinary Medicine will continue to have a profound impact on our world.